Clampable pipe coupling

Pipe joints or couplings – With fluid pressure seal – With separate – encased pipe-gripping means

Reexamination Certificate

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C285S112000, C285S340000, C285S382000, C285S906000

Reexamination Certificate




1. Field of the Invention
The present invention relates to a clampable pipe coupling to axially connect two pipes having a smooth outer surface. The coupling includes split annular or ring-shaped elements that are made from a metal strip. The rings have edge that, in the clamped position, surrounds the pipe ends. The radially inner radial edge of the rings have teeth that extend in the plane of the ring. The free ends of the teeth penetrate into the pipe material when the pipe coupling is in the clamped position. The teeth penetrate into one pipe and extend at an angle relative to the longitudinal axis of the pipe. The teeth also extend at an angle relative to the teeth that engage in the other pipe.
2. Discussion of the Related Arts
Conventional pipe couplings such as, for example, those described in German Reference No. DE 25 55 179B2, have teeth (which are also referred to as “claws”) that are configured like pointed sawteeth. Circumferentially neighboring edges of the sawteeth are V-shaped. A radially inner front face of the sawteeth are inclined relative to the longitudinal axis of the pipes that are joined by the coupling. The pointed tips of these teeth penetrate deeply into the pipe material, even metal pipes, thereby preventing the pipe ends from slipping out of the coupling when the pipes are subject to a high internal pressure. If the teeth are made of a sufficiently rigid material, with increasing internal pressure, the pipes will try to separate, which causes the teeth to move from their radially inclined position relative to the longitudinal axis toward a position where the teeth are normal to the longitudinal axis. In other words, the teeth tend to stand up radially as the pipes attempt to move apart due to internal pressure. As the teeth stand up, their grip and depth of penetration into the pipe around the perimeter of the pipe intensifies, thereby ensuring the axial integrity of the pipe connection in spite of rising internal pressure. But in the case of very high internal pressures, the teeth bend because they are not strong enough. The bending of the teeth is mostly due to their tapered, pointed ends.
Additionally, these conventional sawteeth have radially inner, front surfaces that are inclined rather than perpendicular to the plane of the strip. Thus, producing these sawteeth from a flat metal strip is a complex operation. Similar difficulties are encountered with earlier tooth configurations of pipe couplings, such as those described in German Reference Nos. 27 31 464, 41 11 952, 42 04 762 and 44 11 062, as well as in European Patent Application Nos. 95116480.5 and 95116481.3.
It is an object of the present invention to provide a pipe coupling that has teeth which have greater strength and flexural stiffness, and is easier to produce.
According to an exemplary embodiment of a pipe coupling according to the present invention, this and other objects are achieved with a split circular ring, which has a radially inner edge surrounding the end of the pipe to be clamped. Teeth are disposed at the radially inner edge of the split circular ring. A side of each tooth faces the outside surface of the pipe inserted in this side of the coupling. This side of the tooth has, in the area near or adjacent to the free end of the tooth, at least one indentation. The indentation is stamped into the side of the tooth that faces the adjacent pipe. The indentation causes the material on this side of the tooth to be displaced toward the free end of the tooth.
The displacement of the tooth material in the indentation process causes the teeth to acquire a sharper point, thereby allowing them to penetrate deeper into the pipe material. In addition, it is possible, in a simple manner during the process of punching or die cutting the metal strip, to cut the teeth perpendicular to the plane of the metal strip and to simultaneously stamp the indentations using an appropriate die stamp. In their respective locations, the indentations cause the material of the teeth to become denser and, thus, stronger. An added measure of rigidity is thereby provided by the edge along the indentations resulting in greater flexural stiffness of the serration near the free ends of the teeth.
The indentations preferably have the shape of a section of a hollow sphere, which provides the teeth with very high stiffness and ensures a particularly effective displacement of the tooth material toward the free end of each tooth.

patent: 3632141 (1972-01-01), Larsson
patent: 3746376 (1973-07-01), Gold
patent: 4635975 (1987-01-01), Campbell
patent: 4676531 (1987-06-01), Martin
patent: 25 55 179 B2 (1975-12-01), None
patent: 27 31 465 C2 (1977-07-01), None
patent: 2834046A (1980-02-01), None
patent: 41 11 952 C1 (1991-04-01), None
patent: 42 04 762 C1 (1992-02-01), None
patent: 44 11 062 C1 (1994-03-01), None
patent: 0060309A (1982-09-01), None
patent: 0205896A (1986-12-01), None
patent: 0211158 A1 (1987-02-01), None
patent: 0360946A (1990-04-01), None
patent: 0 769 646 A1 (1995-10-01), None
patent: 0 769 647 A1 (1995-10-01), None
patent: 2662489 (1991-11-01), None
patent: 1582859 (1981-01-01), None
patent: 2287998 (1995-10-01), None
patent: 63-152789 (1988-06-01), None
patent: 1-177405 (1989-07-01), None


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